Window coverings that can be opened and closed are used in a vast number of business buildings and dwellings. Examples of such coverings include horizontal blinds, vertical blinds, pleated shades, roll-up shades, and cellular shades made by, e.g., Spring Industries®, Hunter-Douglas®, and Levellor®.
The present assignee has provided several systems for either lowering or raising a window covering, or for moving the slats of a window covering between open and closed positions. Such systems are disclosed in U.S. Pat. Nos. 6,189,592, 5,495,153, and 5,907,227, incorporated herein by reference. These systems include a motor driven gear box that is coupled to a tilt rod of the window covering. When the motor is energized, the tilt rod rotates clockwise or counterclockwise. These systems can be operated, e.g., with a remote control unit. Using the remote control unit, a user can hold an “Open” button or “Close” button continuously until a desired position of the window covering is reached. Alternatively, the user can depress a single button corresponding to a position of the window covering and the window covering will automatically move to that position, e.g., fully open, half open, close, etc.
Automated systems for opening and closing the window covering to a predetermined location typically require an encoder to be placed somewhere in the gear train. For example, the encoder can be a magnet placed on the output gear with a Hall effect sensor placed just outside the outer periphery of the output gear. As the output gear rotates, the Hall effect sensor senses the magnet and the position of the window covering can be determined. Unfortunately, this type of encoder can have relatively low resolution and as such, the accuracy of any determination of the position of the window covering can be limited.
Accordingly, it is an object of the present invention to provide an remotely controlled and automatic window covering control system having a relatively high resolution position encoder.